a) Field of the Invention
The present invention relates to a semiconductor device, and more particularly to a semiconductor device having an Al alloy wiring.
b) Description of the Related Art
A reduction in the resistance and capacitance of a metal wiring, as well as an improvement in its electromigration resistance, are required due to recent demands for a large scale integration and an increase in the operation speed of a semiconductor device. In order to satisfy these requirements, a wiring which includes a lamination of a Ti and/or TiN film and an Al alloy film is employed.
The stronger Al (111) oriented texture of the Al alloy film, the higher electromigration resistance of the Al alloy film (S. Vaidya and A. K. Sinha, Thin Solid Films, 75 (1981) 253-259). The method of laminating the Al alloy film on a refractory metal film, which is made of a Ta--Al alloy, has been proposed as a plan to strengthen the crystallographic orientation of the (111) face of the Al alloy film (H. Toyoda et al., Proceedings of 32nd International Reliability Physics Symposium, 178 (1994)). According to the Toyoda et al. document, when the Al alloy film is formed on the Ta--Al alloy film, the peak height derived as one corresponding to the (111) face from the X-ray diffraction pattern of the Al alloy film is about four times as great as that when the Al alloy film is formed on the TiN/Ti (TiN: the upper film, Ti: the lower film) film.
Now there is a tendency toward a reduction in the thickness of an Al alloy wiring in order to reduce wire capacitance, etc. If the wiring thickness is reduced, the current density in the wiring will increase, which entails the possibility that electromigration occurs. In consideration of this, a wiring structure having a high electromigration resistance is needed.